The proposed study will determine the most effective dose and regimen for the adiministration of naltrexone in a maintenance treatment program. Long acting preparations of naltrexone complexes will be tested for drug release kinetics and bioavailability in the monkey and the most promising in man. A monitoring system will be developed utilizing plasma and/or parotid saliva for the determination of naltrexone bioavailability. The levels of naltrexone will be determined by gas-liquid chromatography and high-pressure liquid chromatography. The monitoring process is essential for the successful clinical management of subjects in a chemotherapeutic program. Approximately 25 percent of the daily naltrexone dose has not been found, thus attempts will be made to identify new minor metabolites of naltrexone in human subjects, isolate, identify the compound(s) and test their narcotic antagonist activity. The overall importance of the proposed study is to develop naltrexone into a clinically successful therapeutic agent for the treatment of well motivated narcotic addicts and for the prevention of narcotic addiction in juveniles and juvenile experimenters.